Onshore model building using elastic full-waveform inversion on surface and body waves: A case study from Sultanate of Oman

We have determined the potential of the elastic full-waveform inversion (FWI) to overcome some difficult challenges in onshore seismic imaging. The approach allows for simultaneous inversion of surface and body waves and, theoretically, is free from the limitations of traditional dispersion curve analysis and traveltime inversion. Indeed, identification and separation of different wavefield types are not required, and all wave types can be treated within a unified inversion scheme. However, FWI requires a reasonably good initial model, and the sensitivity of the misfit function with respect to the different wave types should be appropriately accounted for. This is the most essential step with onshore seismic data because the ground roll is much more energetic in comparison with the body waves. Our approach is based on a time-offset weighting function to balance the contribution of the different wave types in combination with a conventional frequency continuation approach. We first illustrate the feasibility of our approach on a 2D synthetic example representing a complex geology from south Oman. Then, we develop a 3D real data example from south Oman, where the application of our workflow till 8 Hz plays a pivotal role in retrieving a reliable model and in explaining the entire observed wavefields. In this example, the inversion of the ground roll helps improving the recovery of the shallow part of the earth, and hence better constraining the inversion of the body waves.